In recent years, as a method of protecting a plant from various diseases, there has been widely used a microbial pesticide that uses a microbe antagonistic to pathogens causing various diseases in consideration of safety and sustenance of an effect. In general, the microbial pesticide has an adjuvant added into its formulation in order to prevent a reduction in the effect of an active ingredient in its composition and to improve storage stability. For example, with regard to a Bacillus sp. bacterium that forms spores, in JP 2011-184370 A (Patent Document 1), there is a proposal to add a wettable composition containing a bacterial cell dried product, calcium sulfate, and a surfactant.
In addition, in JP 2004-35421 A (Patent Document 2), there is a proposal of a microbial pesticide containing a microbe, a clay mineral, a surfactant, and a drying agent. As the drying agent, there are specifically disclosed silica gel, calcium chloride, and calcium sulfate anhydrite III.
Meanwhile, in order to improve long-term storage stability of a bacterial cell dried product also in a microbial pesticide formulation that uses a microbe that does not form spores, investigations have been made on adjuvants. For example, JP 2005-325077 A (Patent Document 3) discloses a method involving mixing a Pseudomonas sp. bacterium with trehalose and then lyophilizing the mixture, to thereby obtain a microbe dried product that is satisfactory in terms of recovery rate of viable bacteria and storability as well. As a method further improved on the above-mentioned method, JP 2009-196920 A (Patent Document 4) discloses a method involving mixing a Pseudomonas sp. bacterium with trehalose or sucrose, and with sodium chloride and potassium chloride, and then lyophilizing the mixture, to thereby improve storage stability in a package.
In addition, each of JP 2000-264807 A (Patent Document 5) and JP 2000-264808 A (Patent Document 6) teaches that an Erwinia sp. bacterium or a Pseudomonas sp. bacterium is stored in a stable state by adding zeolite, molecular sieves, silica gel or the like as an adsorbent having an ammonia-adsorbing ability.
Further, as an example of a microbial pesticide formulation containing filamentous fungus spores as an active ingredient and having improved storage stability, JP 2010-143856 A (Patent Document 7) discloses a method involving incorporating amorphous silica into a viable fungal body of a Fusarium sp. fungus, and further adding calcium carbonate and/or magnesium sulfate, to thereby improve storage stability.
However, in each of the inventions of those patent documents, the stability of the microbial pesticide formulation cannot be said to have been sufficiently improved, and there has been a problem in that a plant disease-preventive effect of the microbial pesticide formulation as manufactured cannot be maintained for a long period of time.